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Dai P, Zou M, Cai Z, Zeng X, Zhang X, Liang M. pH Homeodynamics and Male Fertility: A Coordinated Regulation of Acid-Based Balance during Sperm Journey to Fertilization. Biomolecules 2024; 14:685. [PMID: 38927088 PMCID: PMC11201807 DOI: 10.3390/biom14060685] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2024] [Revised: 06/03/2024] [Accepted: 06/10/2024] [Indexed: 06/28/2024] Open
Abstract
pH homeostasis is crucial for spermatogenesis, sperm maturation, sperm physiological function, and fertilization in mammals. HCO3- and H+ are the most significant factors involved in regulating pH homeostasis in the male reproductive system. Multiple pH-regulating transporters and ion channels localize in the testis, epididymis, and spermatozoa, such as HCO3- transporters (solute carrier family 4 and solute carrier family 26 transporters), carbonic anhydrases, and H+-transport channels and enzymes (e.g., Na+-H+ exchangers, monocarboxylate transporters, H+-ATPases, and voltage-gated proton channels). Hormone-mediated signals impose an influence on the production of some HCO3- or H+ transporters, such as NBCe1, SLC4A2, MCT4, etc. Additionally, ion channels including sperm-specific cationic channels for Ca2+ (CatSper) and K+ (SLO3) are directly or indirectly regulated by pH, exerting specific actions on spermatozoa. The slightly alkaline testicular pH is conducive to spermatogenesis, whereas the epididymis's low HCO3- concentration and acidic lumen are favorable for sperm maturation and storage. Spermatozoa pH increases substantially after being fused with seminal fluid to enhance motility. In the female reproductive tract, sperm are subjected to increasing concentrations of HCO3- in the uterine and fallopian tube, causing a rise in the intracellular pH (pHi) of spermatozoa, leading to hyperpolarization of sperm plasma membranes, capacitation, hyperactivation, acrosome reaction, and ultimately fertilization. The physiological regulation initiated by SLC26A3, SLC26A8, NHA1, sNHE, and CFTR localized in sperm is proven for certain to be involved in male fertility. This review intends to present the key factors and characteristics of pHi regulation in the testes, efferent duct, epididymis, seminal fluid, and female reproductive tract, as well as the associated mechanisms during the sperm journey to fertilization, proposing insights into outstanding subjects and future research trends.
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Affiliation(s)
| | | | | | | | - Xiaoning Zhang
- Institute of Reproductive Medicine, Medical School, Nantong University, Nantong 226019, China; (P.D.); (M.Z.); (Z.C.); (X.Z.)
| | - Min Liang
- Institute of Reproductive Medicine, Medical School, Nantong University, Nantong 226019, China; (P.D.); (M.Z.); (Z.C.); (X.Z.)
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Delgado-Bermúdez A, Yeste M, Bonet S, Pinart E. A Review on the Role of Bicarbonate and Proton Transporters during Sperm Capacitation in Mammals. Int J Mol Sci 2022; 23:ijms23116333. [PMID: 35683013 PMCID: PMC9180951 DOI: 10.3390/ijms23116333] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2022] [Revised: 06/01/2022] [Accepted: 06/05/2022] [Indexed: 12/14/2022] Open
Abstract
Alkalinization of sperm cytosol is essential for plasma membrane hyperpolarization, hyperactivation of motility, and acrosomal exocytosis during sperm capacitation in mammals. The plasma membrane of sperm cells contains different ion channels implicated in the increase of internal pH (pHi) by favoring either bicarbonate entrance or proton efflux. Bicarbonate transporters belong to the solute carrier families 4 (SLC4) and 26 (SLC26) and are currently grouped into Na+/HCO3− transporters and Cl−/HCO3− exchangers. Na+/HCO3− transporters are reported to be essential for the initial and fast entrance of HCO3− that triggers sperm capacitation, whereas Cl−/HCO3− exchangers are responsible for the sustained HCO3− entrance which orchestrates the sequence of changes associated with sperm capacitation. Proton efflux is required for the fast alkalinization of capacitated sperm cells and the activation of pH-dependent proteins; according to the species, this transport can be mediated by Na+/H+ exchangers (NHE) belonging to the SLC9 family and/or voltage-gated proton channels (HVCN1). Herein, we discuss the involvement of each of these channels in sperm capacitation and the acrosome reaction.
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Affiliation(s)
- Ariadna Delgado-Bermúdez
- Biotechnology of Animal and Human Reproduction (TechnoSperm), Institute of Food and Agricultural Technology, University of Girona, ES-17003 Girona, Spain; (A.D.-B.); (M.Y.); (S.B.)
- Unit of Cell Biology, Department of Biology, Faculty of Sciences, University of Girona, ES-17003 Girona, Spain
| | - Marc Yeste
- Biotechnology of Animal and Human Reproduction (TechnoSperm), Institute of Food and Agricultural Technology, University of Girona, ES-17003 Girona, Spain; (A.D.-B.); (M.Y.); (S.B.)
- Unit of Cell Biology, Department of Biology, Faculty of Sciences, University of Girona, ES-17003 Girona, Spain
- Catalan Institution for Research and Advanced Studies (ICREA), ES-08010 Barcelona, Spain
| | - Sergi Bonet
- Biotechnology of Animal and Human Reproduction (TechnoSperm), Institute of Food and Agricultural Technology, University of Girona, ES-17003 Girona, Spain; (A.D.-B.); (M.Y.); (S.B.)
- Unit of Cell Biology, Department of Biology, Faculty of Sciences, University of Girona, ES-17003 Girona, Spain
| | - Elisabeth Pinart
- Biotechnology of Animal and Human Reproduction (TechnoSperm), Institute of Food and Agricultural Technology, University of Girona, ES-17003 Girona, Spain; (A.D.-B.); (M.Y.); (S.B.)
- Unit of Cell Biology, Department of Biology, Faculty of Sciences, University of Girona, ES-17003 Girona, Spain
- Correspondence: ; Tel.: +34-972-419-514
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Bernardino RL, Carrageta DF, Sousa M, Alves MG, Oliveira PF. pH and male fertility: making sense on pH homeodynamics throughout the male reproductive tract. Cell Mol Life Sci 2019; 76:3783-3800. [PMID: 31165202 PMCID: PMC11105638 DOI: 10.1007/s00018-019-03170-w] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2018] [Revised: 04/24/2019] [Accepted: 05/29/2019] [Indexed: 02/07/2023]
Abstract
In the male reproductive tract, ionic equilibrium is essential to maintain normal spermatozoa production and, hence, the reproductive potential. Among the several ions, HCO3- and H+ have a central role, mainly due to their role on pH homeostasis. In the male reproductive tract, the major players in pH regulation and homeodynamics are carbonic anhydrases (CAs), HCO3- membrane transporters (solute carrier 4-SLC4 and solute carrier 26-SLC26 family transporters), Na+-H+ exchangers (NHEs), monocarboxylate transporters (MCTs) and voltage-gated proton channels (Hv1). CAs and these membrane transporters are widely distributed throughout the male reproductive tract, where they play essential roles in the ionic balance of tubular fluids. CAs are the enzymes responsible for the production of HCO3- which is then transported by membrane transporters to ensure the maturation, storage, and capacitation of the spermatozoa. The transport of H+ is carried out by NHEs, Hv1, and MCTs and is essential for the electrochemical balance and for the maintenance of the pH within the physiological limits along the male reproductive tract. Alterations in HCO3- production and transport of ions have been associated with some male reproductive dysfunctions. Herein, we present an up-to-date review on the distribution and role of the main intervenient on pH homeodynamics in the fluids throughout the male reproductive tract. In addition, we discuss their relevance for the establishment of the male reproductive potential.
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Affiliation(s)
- Raquel L Bernardino
- Laboratory of Cell Biology, Department of Microscopy, Institute of Biomedical Sciences Abel Salazar and Unit for Multidisciplinary Research in Biomedicine, University of Porto, Porto, Portugal
| | - David F Carrageta
- Laboratory of Cell Biology, Department of Microscopy, Institute of Biomedical Sciences Abel Salazar and Unit for Multidisciplinary Research in Biomedicine, University of Porto, Porto, Portugal
| | - Mário Sousa
- Laboratory of Cell Biology, Department of Microscopy, Institute of Biomedical Sciences Abel Salazar and Unit for Multidisciplinary Research in Biomedicine, University of Porto, Porto, Portugal
| | - Marco G Alves
- Institute of Biomedical Sciences Abel Salazar and Unit for Multidisciplinary Research in Biomedicine, University of Porto, Porto, Portugal
| | - Pedro F Oliveira
- Laboratory of Cell Biology, Department of Microscopy, Institute of Biomedical Sciences Abel Salazar and Unit for Multidisciplinary Research in Biomedicine, University of Porto, Porto, Portugal.
- i3S-Institute for Innovation and Health Research, University of Porto, Porto, Portugal.
- Department of Genetics, Faculty of Medicine, University of Porto, Porto, Portugal.
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Puga Molina LC, Luque GM, Balestrini PA, Marín-Briggiler CI, Romarowski A, Buffone MG. Molecular Basis of Human Sperm Capacitation. Front Cell Dev Biol 2018; 6:72. [PMID: 30105226 PMCID: PMC6078053 DOI: 10.3389/fcell.2018.00072] [Citation(s) in RCA: 143] [Impact Index Per Article: 23.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2018] [Accepted: 06/19/2018] [Indexed: 12/31/2022] Open
Abstract
In the early 1950s, Austin and Chang independently described the changes that are required for the sperm to fertilize oocytes in vivo. These changes were originally grouped under name of “capacitation” and were the first step in the development of in vitro fertilization (IVF) in humans. Following these initial and fundamental findings, a remarkable number of observations led to characterization of the molecular steps behind this process. The discovery of certain sperm-specific molecules and the possibility to record ion currents through patch-clamp approaches helped to integrate the initial biochemical observation with the activity of ion channels. This is of particular importance in the male gamete due to the fact that sperm are transcriptionally inactive. Therefore, sperm must control all these changes that occur during their transit through the male and female reproductive tracts by complex signaling cascades that include post-translational modifications. This review is focused on the principal molecular mechanisms that govern human sperm capacitation with particular emphasis on comparing all the reported pieces of evidence with the mouse model.
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Affiliation(s)
- Lis C Puga Molina
- Instituto de Biología y Medicina Experimental, Consejo Nacional de Investigaciones Científicas y Tecnológicas, Buenos Aires, Argentina
| | - Guillermina M Luque
- Instituto de Biología y Medicina Experimental, Consejo Nacional de Investigaciones Científicas y Tecnológicas, Buenos Aires, Argentina
| | - Paula A Balestrini
- Instituto de Biología y Medicina Experimental, Consejo Nacional de Investigaciones Científicas y Tecnológicas, Buenos Aires, Argentina
| | - Clara I Marín-Briggiler
- Instituto de Biología y Medicina Experimental, Consejo Nacional de Investigaciones Científicas y Tecnológicas, Buenos Aires, Argentina
| | - Ana Romarowski
- Instituto de Biología y Medicina Experimental, Consejo Nacional de Investigaciones Científicas y Tecnológicas, Buenos Aires, Argentina
| | - Mariano G Buffone
- Instituto de Biología y Medicina Experimental, Consejo Nacional de Investigaciones Científicas y Tecnológicas, Buenos Aires, Argentina
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Bernardino RL, Martins AD, Jesus TT, Sá R, Sousa M, Alves MG, Oliveira PF. Estrogenic regulation of bicarbonate transporters from SLC4 family in rat Sertoli cells. Mol Cell Biochem 2015; 408:47-54. [DOI: 10.1007/s11010-015-2481-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2015] [Accepted: 06/13/2015] [Indexed: 11/30/2022]
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Nishigaki T, José O, González-Cota AL, Romero F, Treviño CL, Darszon A. Intracellular pH in sperm physiology. Biochem Biophys Res Commun 2014; 450:1149-58. [PMID: 24887564 PMCID: PMC4146485 DOI: 10.1016/j.bbrc.2014.05.100] [Citation(s) in RCA: 122] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2014] [Accepted: 05/22/2014] [Indexed: 10/25/2022]
Abstract
Intracellular pH (pHi) regulation is essential for cell function. Notably, several unique sperm ion transporters and enzymes whose elimination causes infertility are either pHi dependent or somehow related to pHi regulation. Amongst them are: CatSper, a Ca(2+) channel; Slo3, a K(+) channel; the sperm-specific Na(+)/H(+) exchanger and the soluble adenylyl cyclase. It is thus clear that pHi regulation is of the utmost importance for sperm physiology. This review briefly summarizes the key components involved in pHi regulation, their characteristics and participation in fundamental sperm functions such as motility, maturation and the acrosome reaction.
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Affiliation(s)
- Takuya Nishigaki
- Departamento de Genética del Desarrollo y Fisiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, 62210, Mexico
| | - Omar José
- Departamento de Genética del Desarrollo y Fisiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, 62210, Mexico
| | - Ana Laura González-Cota
- Departamento de Genética del Desarrollo y Fisiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, 62210, Mexico
| | - Francisco Romero
- Departamento de Genética del Desarrollo y Fisiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, 62210, Mexico
| | - Claudia L Treviño
- Departamento de Genética del Desarrollo y Fisiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, 62210, Mexico
| | - Alberto Darszon
- Departamento de Genética del Desarrollo y Fisiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, 62210, Mexico.
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Bernardino RL, Martins AD, Socorro S, Alves MG, Oliveira PF. Effect of Prediabetes on Membrane Bicarbonate Transporters in Testis and Epididymis. J Membr Biol 2013; 246:877-83. [DOI: 10.1007/s00232-013-9601-4] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2013] [Accepted: 09/24/2013] [Indexed: 11/29/2022]
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8
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Liu Y, Wang DK, Chen LM. The physiology of bicarbonate transporters in mammalian reproduction. Biol Reprod 2012; 86:99. [PMID: 22262691 DOI: 10.1095/biolreprod.111.096826] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
HCO(3)(-) plays critically important roles during virtually the entire process of reproduction in mammals, including spermatogenesis, sperm capacitation, fertilization, and development of early stage embryos. Therefore, the acid-base balance in the male and female reproductive tracts must be finely modulated. The fluid milieu in the epididymis is acidic, containing very low concentration of HCO(3)(-). In this acidic low HCO(3)(-) environment, mature sperm are rendered quiescent in the epididymis. In contrast, the luminal fluid in the female uterus and oviduct is alkaline, with very high concentration of HCO(3)(-) that is essential for sperm to fulfill fertilization. HCO(3)(-) transporter of solute carrier 4 (SLC4) and SLC26 families represent the major carriers for HCO(3)(-) transport across the plasma membrane. These transporters play critical roles in intracellular pH regulation and transepithelial HCO(3)(-) transport. The physiological roles of these transporters in mammalian reproduction are of fundamental interest to investigators. Here we review recent progress in understanding the expression of HCO(3)(-) transporters in reproductive tract tissues as well as the physiological roles of these transporters in mammalian reproduction.
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Affiliation(s)
- Ying Liu
- Department of Biological Sciences, Key Laboratory of Molecular Biophysics of Ministry of Education, Huazhong University of Science and Technology School of Life Science and Technology, Wuhan, China
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Hermo L, Pelletier RM, Cyr DG, Smith CE. Surfing the wave, cycle, life history, and genes/proteins expressed by testicular germ cells. Part 4: intercellular bridges, mitochondria, nuclear envelope, apoptosis, ubiquitination, membrane/voltage-gated channels, methylation/acetylation, and transcription factors. Microsc Res Tech 2010; 73:364-408. [PMID: 19941288 DOI: 10.1002/jemt.20785] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
As germ cells divide and differentiate from spermatogonia to spermatozoa, they share a number of structural and functional features that are common to all generations of germ cells and these features are discussed herein. Germ cells are linked to one another by large intercellular bridges which serve to move molecules and even large organelles from the cytoplasm of one cell to another. Mitochondria take on different shapes and features and topographical arrangements to accommodate their specific needs during spermatogenesis. The nuclear envelope and pore complex also undergo extensive modifications concomitant with the development of germ cell generations. Apoptosis is an event that is normally triggered by germ cells and involves many proteins. It occurs to limit the germ cell pool and acts as a quality control mechanism. The ubiquitin pathway comprises enzymes that ubiquitinate as well as deubiquitinate target proteins and this pathway is present and functional in germ cells. Germ cells express many proteins involved in water balance and pH control as well as voltage-gated ion channel movement. In the nucleus, proteins undergo epigenetic modifications which include methylation, acetylation, and phosphorylation, with each of these modifications signaling changes in chromatin structure. Germ cells contain specialized transcription complexes that coordinate the differentiation program of spermatogenesis, and there are many male germ cell-specific differences in the components of this machinery. All of the above features of germ cells will be discussed along with the specific proteins/genes and abnormalities to fertility related to each topic.
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Affiliation(s)
- Louis Hermo
- Department of Anatomy and Cell Biology, Faculty of Medicine, McGill University, 3640 University Street, Montreal, QC Canada H3A 2B2.
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Satake N, Elliott RMA, Watson PF, Holt WV. Sperm selection and competition in pigs may be mediated by the differential motility activation and suppression of sperm subpopulations within the oviduct. J Exp Biol 2006; 209:1560-72. [PMID: 16574812 DOI: 10.1242/jeb.02136] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
SUMMARYWhen spermatozoa from two or more boars are mixed and females inseminated,the resulting litters are often skewed in favour of one male but there is currently no satisfactory physiological explanation for this effect. However,to reach the oocytes, the spermatozoa must enter the oviduct where they are exposed to factors that modulate their activity. They either become sequestered within the oviductal sperm reservoir or bypass the reservoir and proceed towards the oocytes. The oviduct may therefore hold the key to mammalian sperm selection, thereby explaining why laboratory tests of sperm function, performed on whole ejaculates, are unable to account for the boar-specific skewing effects. We have previously shown that boar sperm motility is highly stimulated by bicarbonate, a naturally abundant component of oviductal fluid. Using motility-based sperm subpopulation analysis, we show here that the relative sizes of bicarbonate-responsive and unresponsive sperm subpopulations vary between individual boars. Proteins derived from oviduct epithelial plasma membranes suppress the activation response and modify sperm movement trajectories in a subpopulation-specific and dose-dependent manner. The suppression response varies between boars and some spermatozoa remain unsuppressed in the presence of oviductal proteins. When boars are ranked according to their susceptibility to bicarbonate-induced stimulation, rankings differ depending upon the presence or absence of oviductal proteins. The suppression response is not caused by inhibition of bicarbonate uptake; on the contrary this is enhanced by oviductal proteins. We suggest that the boar-specific and sperm subpopulation-specific interactions between sperm motility activation and suppression responses are likely to result in sperm selection before the spermatozoa meet the oocytes.
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Affiliation(s)
- Nana Satake
- Institute of Zoology, Zoological Society of London, Regent's Park, UK
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Medina JF, Recalde S, Prieto J, Lecanda J, Saez E, Funk CD, Vecino P, van Roon MA, Ottenhoff R, Bosma PJ, Bakker CT, Elferink RPJO. Anion exchanger 2 is essential for spermiogenesis in mice. Proc Natl Acad Sci U S A 2003; 100:15847-52. [PMID: 14673081 PMCID: PMC307656 DOI: 10.1073/pnas.2536127100] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Na+-independent anion exchangers (AE) mediate electroneutral exchange of Cl- for HCO3- ions across cell membranes, being involved in intracellular pH and cell volume regulation and in transepithelial hydroionic fluxes. Bicarbonate activation of adenylyl cyclase is known to be necessary for sperm motility and sperm capacitation, and a few studies have suggested a possible role of AE carriers in reproduction. Among the four AE genes identified in mammals thus far, only Ae2 (Slc4a2) has been determined to be expressed in the male reproductive system, especially in developing spermatozoa and in epididymal epithelium. Most AE genes drive alternative transcription, which in mouse Ae2 results in several Ae2 isoforms. Here, we generated mice carrying a targeted disruption of Ae2 that prevents the expression of the three AE2 isoforms (Ae2a, Ae2b1, and Ae2b2) normally found in mouse testes. Male Ae2-/- mice (but not female Ae2-/- mice) are infertile. Histopathological analysis of Ae2-/- testes shows an interruption of spermiogenesis, with only a few late spermatids and a complete absence of spermatozoa in the seminiferous tubules. The number of apoptotic bodies is increased in the seminiferous tubules and in the epididymis, which also shows squamous metaplasia of the epididymal epithelium. Our findings reveal an essential role of Ae2 in mouse spermiogenesis and stress the recently postulated involvement of bicarbonate in germ-cell differentiation through the bicarbonate-sensitive soluble-adenylyl-cyclase pathway.
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Affiliation(s)
- Juan F Medina
- Division of Hepatology and Gene Therapy, University Hospital/School of Medicine, Fundación para la Investigación Medica Aplicada, University of Navarra, E-31008 Pamplona, Spain.
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Holappa K, Kellokumpu S. Targeting of the AE2 anion exchanger to the Golgi apparatus is cell type-dependent and correlates with the expression of Ank(195), a Golgi membrane skeletal protein. FEBS Lett 2003; 546:257-64. [PMID: 12832051 DOI: 10.1016/s0014-5793(03)00597-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Sodium-independent anion exchangers (AE1-4) show remarkable variability in their tissue-specific expression and subcellular localization. Currently, isoform-specific targeting mechanisms are considered to be responsible for this variable localization. Here, we report that targeting can also be cell type-specific. We show that the full-length AE2 protein and its green fluorescent protein- or DsRed-tagged variants localize predominantly either to the Golgi apparatus in COS-7 cells, or to the plasma membrane in HeLa cells. This alternative targeting did not seem to result from either translational or post-translational differences, but rather from differential expression of at least one of the Golgi membrane skeletal proteins, ankyrin(195) (Ank(195)), between the two cell types. Comparative studies with several different cell lines revealed that the Golgi localization of the AE2 protein correlated strictly with the expression of Ank(195) in the cells. The two Golgi-associated proteins also co-localized well and similarly resisted detergent extraction in the cold, whereas the plasma membrane-localized AE2 in Ank(195)-deficient cells was mostly detergent-soluble. Collectively, our results suggest that Ank(195) expression is a key determinant for the variable and cell type-dependent localization of the AE2 protein in the Golgi apparatus in mammalian cells.
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Affiliation(s)
- Katja Holappa
- University of Oulu, Department of Biochemistry, PO Box 3000, FIN-90014 Oulu, Finland
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Kaunisto K, Parkkila S, Rajaniemi H, Waheed A, Grubb J, Sly WS. Carbonic anhydrase XIV: luminal expression suggests key role in renal acidification. Kidney Int 2002; 61:2111-8. [PMID: 12028451 DOI: 10.1046/j.1523-1755.2002.00371.x] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
BACKGROUND Carbonic anhydrase (CA) plays a fundamental role in regulation of systemic acid-base homeostasis by facilitating urinary acidification. Four CA isozymes (CA II, IV, XII, XIV) have been identified in kidney. Until now, luminal CA IV, a GPI-anchored isozyme, was thought to mediate most bicarbonate absorption. Although CA XIV mRNA has been demonstrated in mouse and human kidney, the localization of this newly discovered CA has not been established. METHODS RT-PCR and Western blot analyses were used to demonstrate CA XIV mRNA and protein in extracts of cortex and medulla of mouse kidney. Polyclonal antibodies against mouse CA XIV were utilized for immunofluorescence to examine the pattern of expression of CA XIV in the nephron of both rat and mouse kidney. RESULTS Immunofluorescence staining showed abundant expression of CA XIV in apical plasma membranes of the S1 and S2 segments of proximal tubules, and weaker staining in the basolateral membranes. Also, strong staining was seen in the initial portion of the thin descending limb of Henle. These results show that luminal CA XIV is strongly expressed in regions of the rodent nephron that have been thought to be important in urinary acidification. Staining for CA XIV and CA IV in the same sections showed some areas of co-expression, but also some areas where each was expressed without the other. CONCLUSIONS Luminal CA XIV may account for a substantial fraction of the bicarbonate reabsorption previously attributed to CA IV. If so, CA XIV and CA IV may be functionally redundant.
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Affiliation(s)
- Kari Kaunisto
- Department of Anatomy and Cell Biology, University of Oulu, Oulu, Finland
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Parkkila S, Kivelä AJ, Kaunisto K, Parkkila AK, Hakkola J, Rajaniemi H, Waheed A, Sly WS. The plasma membrane carbonic anhydrase in murine hepatocytes identified as isozyme XIV. BMC Gastroenterol 2002; 2:13. [PMID: 12033992 PMCID: PMC115862 DOI: 10.1186/1471-230x-2-13] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/22/2002] [Accepted: 05/21/2002] [Indexed: 02/06/2023] Open
Abstract
BACKGROUND Biochemical and histochemical studies have both previously indicated plasma membrane-associated carbonic anhydrase (CA) activity in hepatocytes which has been assumed to be CA IV. However, immunohistochemical data did not support this assignment. Recent northern blotting results indicated the presence of mRNA for the most recently discovered membrane-bound CA isozyme, CA XIV, in the liver. The present study was designed to examine whether CA XIV could contribute to the CA activity described in the hepatocytes. METHODS Tissue samples from mouse liver were subjected to immunohistochemical staining using the antibodies raised against recombinant mouse CA XIV and CA IV. RT-PCR and western blotting were also performed for CA XIV. RESULTS A strong immunofluorescent signal was observed in the plasma membrane of mouse hepatocytes. Although CA XIV was expressed on both the apical and basolateral surfaces, the staining was more prominent at the apical (canalicular) membrane domain. The expression of CA XIV in the liver was confirmed by RT-PCR and western blotting. CONCLUSIONS The presence of CA XIV in the hepatocyte plasma membrane places this novel enzyme at a strategic site to control pH regulation and ion transport between the hepatocytes, sinusoids and bile canaliculi.
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Affiliation(s)
- Seppo Parkkila
- Department of Clinical Chemistry, 90014 University of Oulu, Finland; Institute of Medical Technology, University of Tampere and Tampere University Hospital, 33014 Tampere, Finland
| | - Antti J Kivelä
- Department of Anatomy and Cell Biology, 90014 University of Oulu, Finland
| | - Kari Kaunisto
- Department of Anatomy and Cell Biology, 90014 University of Oulu, Finland
- Department of Pediatrics, 90014 University of Oulu, Finland
| | - Anna-Kaisa Parkkila
- Department of Neurology, Tampere University Hospital, 33521 Tampere, Finland
| | - Jukka Hakkola
- Department of Pharmacology and Toxicology, 90014 University of Oulu, Finland
| | - Hannu Rajaniemi
- Department of Anatomy and Cell Biology, 90014 University of Oulu, Finland
| | - Abdul Waheed
- Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, 1402 S. Grand Blvd, St. Louis, MO 63104, USA
| | - William S Sly
- Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, 1402 S. Grand Blvd, St. Louis, MO 63104, USA
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Holappa K, Suokas M, Soininen P, Kellokumpu S. Identification of the full-length AE2 (AE2a) isoform as the Golgi-associated anion exchanger in fibroblasts. J Histochem Cytochem 2001; 49:259-69. [PMID: 11156694 DOI: 10.1177/002215540104900213] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Na(+)-independent Cl(-)/HCO(3)(-) exchangers (AE1, AE2, AE3) are generally known as ubiquitous, multispanning plasma membrane proteins that regulate intracellular pH and transepithelial acid-base balance in animal tissues. However, previous immunological evidence has suggested that anion exchanger (AE) proteins may also be present in intracellular membranes, including membranes of the Golgi complex and mitochondria. Here we provide several lines of evidence to show that an AE protein is indeed a resident of the Golgi membranes and that this protein corresponds to the full-length AE2a isoform in fibroblasts. First, both the N- and C-terminal antibodies to AE2 (but not to AE1) detected an AE protein in the Golgi membranes. Golgi localization of this AE2 antigen was evident also in cycloheximide-treated cells, indicating that it is a true Golgi-resident protein. Second, our Northern blotting and RT-PCR analyses demonstrated the presence of only the full-length AE2a mRNA in cells that show prominent Golgi staining with antibodies to AE2. Third, antisense oligonucleotides directed against the translational initiation site of the AE2a mRNA markedly inhibited the expression of the endogenous AE2 protein in the Golgi. Finally, transient expression of the GFP-tagged full-length AE2a protein resulted in predominant accumulation of the fusion protein in the Golgi membranes in COS-7 and CHO-K1 cells. Golgi localization of the AE2a probably involves its oligomerization and/or association with the recently identified Golgi membrane skeleton, because a substantial portion of both the endogenous AE2a and the GFP-tagged fusion protein resisted detergent extraction in cold. (J Histochem Cytochem 49:259-269, 2001)
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Affiliation(s)
- K Holappa
- Department of Anatomy and Cell Biology, University of Oulu, Oulu, Finland.
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Lecanda J, Urtasun R, Medina JF. Molecular cloning and genomic organization of the mouse AE2 anion exchanger gene. Biochem Biophys Res Commun 2000; 276:117-24. [PMID: 11006093 DOI: 10.1006/bbrc.2000.3439] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The molecular organization of the AE2 (SLC4A2) gene, a member of the multigene family encoding sodium-independent chloride/bicarbonate anion exchangers, has previously been described in both humans and rats. In these two species, AE2 shows alternate promoter usages and tissue-specific expression of isoforms in a similar, but not identical, fashion. Here we report the molecular cloning and organization of the entire mouse AE2 gene. The gene consists of 23 exons and 22 introns and spans about 17 kb. Moreover, it drives transcription of N-terminal truncated isoforms from alternate promoter sequences in a way analogous to that described for rat and/or human orthologs. Thus, sequences within intron 2 function as overlapping alternate promoters for truncated isoforms AE2b(1) and AE2b(2), and sequences of intron 5 drive transcription of isoforms AE2c(1) and AE2c(2). Each of these variants has a specific alternative first exon, while remaining exons are common to the complete form of the message AE2a, the diversity at 5' leading to different N-termini in corresponding encoded proteins. As expected, mouse AE2 promoter sequences and the patterns of tissue expression of AE2 isoforms resemble rat counterparts more closely than human ones.
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Affiliation(s)
- J Lecanda
- Laboratory of Molecular Genetics, University Clinic and Medical School, Pamplona, E-31008, Spain
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